Field of the Invention
The present invention relates to an ink jet recording method and an ink jet recording apparatus.
Description of the Related Art
An ink jet recording method enables recording of images on various recording media. In order to produce better images, various inks, such as inks suited for recording photographic quality images on glossy paper and the like and inks suited for recording documents on plain paper and the like, have been developed according to purposes.
In recent years, the ink jet recording method is also used, for example, for recording business documents containing characters, diagrams, and the like on plain paper or similar recording media, and has been markedly frequently used for such purposes.
As the technique of the ink jet recording method develops, ink jet recording apparatuses are required to have higher durability and reliability in order to be usable for a long period of time and also to enable recording of a larger number of images, thereby achieving high productivity.
In order to improve the productivity, an ink jet recording apparatus in which a main tank and a sub tank are provided as ink storage portions and are connected through an ink supply tube is known, for example. The sub tank is typically provided on the top of a recording head installed on a carriage. When an ink jet recording apparatus having the above-mentioned structure is used to record images, an ink supply tube that has one end connected to the main tank and the other end connected to the sub tank is pulled around in the apparatus by bi-directional scanning of the carriage. On this account, the material of the tube is selected from the materials having sufficient flexibility to withstand the bi-directional scanning of the carriage. In particular, recent ink jet recording apparatuses have been further downsized, and members of the apparatuses are required to be arranged in a compact space. To meet this demand, the tube is required to have higher flexibility.
From a tube filled with an ink, components such as water pass through the tube to evaporate depending on the material of the tube. Such a phenomenon increases the viscosity of the ink due to evaporation of water and the like, and this is likely to deteriorate ejection stability of the ink. In addition, the composition of the ink is changed due to a reduction of water content and the like, and this is likely to cause problems such as quality deterioration of images recorded. In other words, the material of a tube is required to be selected in consideration of images to be recorded. Meanwhile, when air passes through a tube from the outside to the inside and is mixed with an ink, the dissolved air amount in the ink increases. When the air having dissolved in the ink forms bubbles due to any stimulus, the ink in the tube contains the bubbles. When the ink containing bubbles is supplied to a recording head, the bubbles are likely to cause problems including ink ejection failure. In other words, the material of a tube is required to be selected also in consideration of ink ejection stability.
As an ink supply tube, a tube having higher moisture barrier performance, air barrier performance, and kink resistance is disclosed. The tube is formed of a resin material including a thermoplastic elastomer containing a particular block copolymer and a lubricant component at a particular ratio (Japanese Patent Application Laid-Open No. 2012-051368). In order to improve the ejection stability of an ink, ink jet recording apparatuses are disclosed. In the apparatuses, the moisture permeability of members constituting the recording apparatus, such as a main tank, a recording head, and a tube, the viscosity and the surface tension of an ink after evaporation are controlled within particular ranges, for example (Japanese Patent Application Laid-Open No. 2007-196466 and Japanese Patent Application Laid-Open No. 2004-136580).
In order to improve the productivity, the inventors of the present invention have studied the material of an ink supply tube by using an ink jet recording apparatus having a structure in which a main tank and a sub tank are provided as the ink storage portions and these tanks are connected through an ink supply tube. The result reveals that images recorded are unlikely to be deteriorated even when the tube disclosed in Japanese Patent Application Laid-Open No. 2012-051368 is used and an ink is ejected over a long period of time.
In a typical ink jet recording apparatus, a water head difference of liquid levels, a negative pressure generation member, or the like is used to maintain a negative pressure of an ink supply system, thereby preventing an ink from leaking from an ejection orifice on a recording head. In other words, the ink supply system is required to maintain a negative pressure constantly. In the ink jet recording apparatus having the structure in which a main tank and a sub tank are provided as the ink storage portions and these tanks are connected through an ink supply tube, the ink supply system is in an open system condition when an ink is injected into the main tank. On this account, the negative pressure of the ink supply system is not maintained when an ink is injected, and accordingly the ink may leak from an ejection orifice on a recording head. In order to maintain a negative pressure of the ink supply system even when an ink is injected into a main tank, a mechanism of blocking an ink supply tube is required to be provided.
However, the study by the inventors of the present invention has revealed the following new problem. When the ink supply tube disclosed in Japanese Patent Application Laid-Open No. 2012-051368 is blocked when an ink is injected into a main tank, the crept tube remains even after the release of blocking, and it is difficult to stably supply the ink.
An object of the present invention is thus to solve the problems caused when an ink jet recording apparatus including a main tank, a sub tank, an ink supply tube connecting the tanks, and a mechanism of blocking the ink supply tube is used over a long period of time. In other words, the present invention aims to provide an ink jet recording method that enables the above ink jet recording apparatus to maintain good ink ejection stability even when the ink jet recording apparatus is used over a long period of time and to stably supply an ink even after release of blocking of the ink supply tube. The present invention also aims to provide an ink jet recording apparatus used in the ink jet recording method.